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Tuning the reactivity of mononuclear nonheme manganese(IV)-oxo complexes by triflic acid

Title
Tuning the reactivity of mononuclear nonheme manganese(IV)-oxo complexes by triflic acid
Authors
Chen, JunyingYoon, HeejungLee, Yong-MinSeo, Mi SookSarangi, RitimuktaFukuzumi, ShunichiNam, Wonwoo
Ewha Authors
남원우Shunichi Fukuzumi이용민서미숙
SCOPUS Author ID
남원우scopus; Shunichi Fukuzumiscopus; 이용민scopusscopus; 서미숙scopusscopus
Issue Date
2015
Journal Title
CHEMICAL SCIENCE
ISSN
2041-6520JCR Link2041-6539JCR Link
Citation
vol. 6, no. 6, pp. 3624 - 3632
Publisher
ROYAL SOC CHEMISTRY
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Triflic acid (HOTf)-bound nonheme Mn(IV)-oxo complexes, [(L)Mn-IV(O)](2+)-(HOTf)(2) (L = N4Py and Bn-TPEN; N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine and Bn-TPEN = N-benzyl-N,N',N'-tris-(2-pyridylmethyl)ethane-1,2-diamine), were synthesized by adding HOTf to the solutions of the [(L) Mn-IV(O)](2+) complexes and were characterized by various spectroscopies. The one-electron reduction potentials of the Mn-IV(O) complexes exhibited a significant positive shift upon binding of HOTf. The driving force dependences of electron transfer (ET) from electron donors to the Mn-IV(O) and Mn-IV(O)-(HOTf)(2) complexes were examined and evaluated in light of the Marcus theory of ET to determine the reorganization energies of ET. The smaller reorganization energies and much more positive reduction potentials of the [(L) Mn-IV(O)](2+)-(HOTf)(2) complexes resulted in greatly enhanced oxidation capacity towards one-electron reductants and para-X-substituted-thioanisoles. The reactivities of the Mn(IV)-oxo complexes were markedly enhanced by binding of HOTf, such as a 6.4 x 10(5)-fold increase in the oxygen atom transfer (OAT) reaction (i.e., sulfoxidation). Such a remarkable acceleration in the OAT reaction results from the enhancement of ET from para-X-substituted-thioanisoles to the Mn-IV(O) complexes as revealed by the unified ET driving force dependence of the rate constants of OAT and ET reactions of [(L) Mn-IV(O)](2+)-(HOTf)(2). In contrast, deceleration was observed in the rate of H-atom transfer (HAT) reaction of [(L)Mn-IV(O)](2+)-(HOTf)(2) complexes with 1,4-cyclohexadiene as compared with those of the [(L)Mn-IV(O)](2+) complexes. Thus, the binding of two HOTf molecules to the Mn-IV(O) moiety resulted in remarkable acceleration of the ET rate when the ET is thermodynamically feasible. When the ET reaction is highly endergonic, the rate of the HAT reaction is decelerated due to the steric effect of the counter anion of HOTf.
DOI
10.1039/c5sc00535c
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자연과학대학 > 화학·나노과학전공 > Journal papers
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